Typically, various methods and devices have been developed as measures for improving rivers and lakes. These methods and devices include, for example, decomposition of contaminated substances by utilization of microorganisms, physical treatment utilizing, e.g., ozone or ultrasonic waves, and adsorption or filtration by charcoal, bamboo charcoal, or activated charcoal.
Moreover, a national census (a river version) on river environment by the Ministry of Land, Infrastructure, Transport, and Tourism has been reviewed. For example, part of biological assessment and river environment base map preparation assessment having been revised in 2006 has been further revised two years ago, i.e., in March, 2012. As described above, an effort against a water quality environment problem has been just enhanced.
However, it is extremely difficult to improve and purify water in rivers and oceans where contamination has progressed over a long period of time. Without a large-sized water purification treatment device and a long-term process, it is difficult to recover the rivers and the oceans. Specifically, in the case of aiming for water purification in large lakes and oceans, a significant cost is also a problem.
In view of these problems, various techniques have been typically proposed. The inventor(s) of the present application has addressed the problems, and has proposed the techniques. For example, “the method and device for efficiently decomposing and annihilating harmful substances by generating, in contaminated water, many air bubbles taking in negative ions have been proposed (see Patent Literature 1).” According to such an invention, a collision ionization phenomenon occurs, and ultrafine air bubbles are drained to rivers and lakes through an expanded annular opening of a diffuser panel. Further, the drained ultrafine air bubbles can detoxify, upon vanishing, the harmful substances by a cavitation effect. Then, the detoxified treatment residual substances float to a water surface by interfacial aggregation action. These substances can be sucked and processed on the ground. This prevents, at the same time as improvement of the rivers and the lakes, the detoxified residual substances from settling down to bottom portions of the rivers and the lakes and forming bottom sediment sludge. Thus, a river/lake water quality improvement effect is significantly high.
However, contamination has been currently grown into a serious problem even though an attempt has been typically made to improve contaminated water in rivers and lakes by various methods described above. A reason for such a situation is the lack of the method for removing the treatment residual substances detoxified by decomposition, adsorption, filtration, or the like of the harmful contaminated substances. For this reason, there is a problem that the treatment residual substances become the source of generation of a large amount of plankton and the like. The method and the device according to Patent Literature 1 employ a technique which can solve these problems. However, a long period of one to two months is required for such treatment. Thus, the prompt decomposition and removal are not sufficiently performed. Consequently, the problem still remains.
In addition, the following invention and the like have been made. Patent Literature 2 discloses “a microbubble formation device for dissolving microbubbles of gas in liquid.” Patent Literature 3 discloses “a water improvement method utilizing bacteria and aquaculture method and system utilizing bacteria.” Alternatively, Patent Literature 4 discloses “a contaminated substance treatment device and a contaminated substance treatment method, the device including an electrolysis water manufacturing device configured to manufacture alkaline electrolysis water and acidic electrolysis water and a decontamination device configured to decontaminate a decontamination target object.” The decontamination device uses, as a cleaning solution, either of the alkaline electrolysis water and the acidic electrolysis water, both being manufactured by the electrolysis water manufacturing device. Further, Patent Literature 5 discloses “ceramic for a water purification device configured to improve water, the ceramic being incorporated in the water purification device and being configured such that the shape of the ceramic alone is, e.g., a polyhedron surrounded by seven or more planes.” Each of these inventions has a unique advantage, and has been considered as effective. However, a water purification effect is unique to each invention. For this reason, it has been demanded to propose a technique of a water purification device configured so that these effects can be exerted in a combined manner with a low cost.